Photographic silver halide emulsions with increased sensitivity



United States Patent Oflice 3,551,158 Patented Dec. 29, 1970 3,551,158 PHOTOGRAPHIC SILVER HALIDE EMULSIONS WITH INCREASED SENSITIVITY Harald Huckstadt, Cologne, Stammheim, August Randolph, Leverkusen, Wilhelm Saleck, Schildgen-Bergendorf-Gladbach, and Erwin Ranz, Leverkusen, Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Dec. 20, 1966, Ser. No. 603,168 Claims priority, application Germany, Dec. 28, 1965, A 51,190 Int. Cl. G03c 1/28 US. Cl. 96-107 5 Claims ABSTRACT OF THE DISCLOSURE Photographic silver halide emulsions having their sensitivity increased by the combination of a polyethylene oxide sensitizer and a sulfonium salt wherein R=a branched or unbranched alkyl or alkenyl radical containing up to 6 carbon atoms which. may be interrupted by hetero atoms and substituted by at least one hydroxyl, carboxyl or epoxy group;

Z=an alkylen radical having up to 18 carbon atoms that can be substituted with at least one hydroxyl, carboxyl or epoxy group, and can be interrupted by a hetero atom such as at least one oxygen atom, or aralkylen; and

X=an anion.

The present invention relates to photographic silver halide emulsions chemically sensitized by the addition of heterocyclic sulfur compounds.

A number of methods have been described for improving the sensitivity of photographic silver halide emulsions other than by optical or spectral sensitization with sensitizing dyes incorporated in the emulsion. The incorporation of such dyes in the emulsion increases the optical or spectral range of sensitivity, and for this reason such dyes are commonly referred to as optical or spectral sensitizing dyes. Contrary to optical or spectral sensitizers the so-called chemical sensitizers are believed to react with silver halide to form, on the surface of the silver halide grain, sensitivity specks the chemical nature of which depends on the kind of the chemical sensitizer. The sensitivity of silver halide emulsions can be increased by chemical ripening or after-ripening during the preparation of the emulsion, by either prolonging the ripening time or by the addition of suitable substances such as compounds of noble metals or thiosulfate or other sulfur compounds. According to another method customarily employed the sensitivity of a photographic emulsion can be increased by the addition of development accelerators or chemical sensitizers to the emulsion, usually when it is completely ripened.

Suitable development accelerators are, for example, compounds containing onium groups (for example, quaternary ammonium or phosphonium and ternary sulfonium salts) and polyalkylene oxides and derivatives of polyalkylene oxides.

The process of chemical sensitization, however, reaches a limit beyond which further addition of sensitizing compounds or of prolonged digestion in the presence of a sensitizer, merely increases the undesired fog of the photographic emulsions.

In particular with respect to polyalkylene oxide sensitizers, many attempts have been made to increase the sensitizing action by modifying the chemical structure or by using them in combination with other compounds. However, in practice, none of these compounds completely meet the requirements as regards producing a satisfactory increase in sensitivity without concomitant increases in fog or poor keeping qualities.

The object of the present invention is to provide new chemical sensitizers which do not suffer the above disadvantages. Another object is to provide photographic silver halide emulsions having increased sensitivity and satisfactory keeping qualities.

We now have found the sensitivity of the silver halide emulsion chemically sensitized with polyethylene oxide or derivatives thereof can be further increased by the addition of an aliphatic or araliphatic sulfonium salt, the aliphatic radicals of which are substituted by hydroxyl, carboxyl or epoxy groups.

The sulfonium salts correspond to the following formulae:

RS X or R SZ-S R2X ea ea wherein:

R=a branched or unbranched alkyl or alkenyl radical containing up to 6 C-atoms, which may be interrupted by hetero atoms, in particular oxygen and which is substituted by at least one hydroxyl, carboxyl or epoxy p;

Z=(1) an alkylene radical having up to 18 C-atoms, preferably up to 6 C-atoms, which alkylene radical may be substituted by at least one hydroxyl, carboxyl or epoxy group or which may be interrupted by hetero atoms, in particular at least one ether oxygen atom to give, for instance, ethylene ether or polyethylene ether groupings, or (2) aralkylene such as xylylene, and

X=any anion, for example, halide ions, such as chloride or bromide, perchlorate, paratoluenesulfonate or methane sulfonate ions.

The above mentioned groupings may, of course, carry further substituents provided that they neither impair the increase in the sensitivity which the compounds of the present invention provide nor have any adverse eifects on the photographic properties of the emulsions. The following compounds have proved to be especially suitable:

The sulfonium salts used according to the invention can be prepared in known manner. They may usually be obtained by reacting suitable sulfides, such as thiodiglycol, with monoor dihalides. The preparation of two compounds is given in detail below. The other compounds can be prepared in a similar manner.

COMPOUND II 12.2 g. (0.1 mol) of thiodiglycol and 25.5 g. (0.3 rnol) of ethylene chlorohydrin are heated with 60 ml. of Water for 13 hours on a water bath. The water is then boiled off and the solid residue is recrystallized from alcohol. Yield g., M.P. 126127 C.

COMPOUND V 12.2 g. (0.1 mol) thiodiglycol and 8.7 g. (0.05 mol) 1,4-di-(chloromethyl)-benzene are boiled under reflux for 6 hours in 250 ml. of methanol. The solvent is then distilled oil and the solid residue is recrystallized from methanol/water. Yield: 5.5 g., M.P. 133-135 C.

Any polyalkylene oxides or derivatives thereof can be used in combination with the above sulfonium compounds. The molecular weight of these polyalkylene oxides should be above 300, and preferably from 1500 to 10,000. Compounds of this type have, for example, the following formula R stands for hydrogen or alkyl having preferably up to 18 carbon atoms such as ethyl or dodecyl, or an acyl group which is preferably derived from an aliphatic carboxylic acid having up to 18 carbon atoms such as lauric acid or oleic acid, or a radical of the phenyl group such as phenyl or alkyl substituted phenyl, for instance, p-dodecylphenyl; and

n is an integer from 8 to 200.

Polyethylene oxides of this type have been described in U.S. Pats. 2,240,472 and 2,400,532. Other suitable chemical sensitizers are derivatives of phosphoric acid which contain polyalkylene oxide chains. Products of this type have been described in British patent specifications 1,045,183 and 1,045,184 or in French patent specification 1,423,680.

This latter class of compounds include condensation products of spirocyclic pentaerythritol-di-phosphoric acid monohalides and polyethylene glycols containing about 3 4 to ethylene oxide units. They correspond to the following general formula wherein:

R represents a hydrogen atom or an alkylene oxide chain containing 3 to 100 alkylene oxide units,

y is an integer from 1 to 100 and m an integer from 3 to 100*.

This group of chemical sensitizers also includes condensation products of amidophosphoric acid derivatives with polyethylene glycols of the type described above. Such compounds are represented by the following formula:

Furthermore, the sulfonium salts according to the invention may be advantageously used in combination with the cross-linked or non-cross-linked water-soluble quaternation products of tertiary polyamines with bifunctional polyalkylene oxide derivatives, which quaternation products have been described in German patent application No. A 50,595 corresponding to U.S. application Ser. No. 591,974, filed Nov. 4, 1966.

The addition of the compounds according to the invention in combination with polyalkylene oxides or polyal-kylene oxide derivatives to the silver halide emulsion results in a higher sensitivity than is achieved by the addition of the only one such component. There is thus a genuine synergistic eifect.

The compounds according to the invention can be used in any silver halide emulsions. Silver halides which may be used are silver chloride, silver bromide or mixtures thereof, if desired with a small amount of silver iodide of up to 10 mols percent. The silver halides can be dispersed in the usual hydrophilic compounds, for example, in carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides, and preferably in gelatin.

The preparation of photographic silver halide emulsions include 3 separate steps: (1) emulsification and physical ripening which is also called Ostwald ripening, (2) the freeing of the emulsion of excess water soluble salts, usually by washing with water and drying; and (3) the after ripening which is also called chemical ripening to obtain increased emulsion speed or general sensitivity.

The sensitizer of the present invention can be added to the emulsion before, during or after the chemical ripening or they can be added immediately prior to the casting.

Furthermore, the compounds can be added to the developer solution with similar efiect.

The compounds according to the invention are added to the emulsion in quantities of 0.3 to 30 g. per mol of silver halide, preferably 0.3 to 3 g. per mol of silver halide. The above quantities correspond to a concentration of 0.1 to g. per liter of emulsion, preferably 0.1 to 1 g. per liter of emulsion.

The polyalkylene oxides or polyalkylene oxide derivatives are used in the usual quantity. The concentration of the polyalkylene oxides can vary within wide limits depending upon the effect desired, and the nature of the emulsion used. In general, the addition of preferably 0.3 to 3 g. of polyalkylene oxide or derivatives thereof per mol of silver halide is suflicient.

The sensitizers can be dissolved in water or a solvent miscible with water or a mixture of water and water miscible solvents and added in this form to the emulsion. The solvent is not critical and should be selected so that it should have no harmful eifect to the photographic properties of the silver halide emulsion.

The optimum amount for any sensitizer of the present invention can be determined for any particular emulsion by running a series of comparison tests in which the quantity of the sensitizer is varied over a given range. Exposure of the emulsion containing the sensitizer'in a manner well known and measuring of the sensitivity in conventional apparatuses will reveal most advantageous concentrations. Such technic is well understood by those skilled in the art.

The emulsions may also contain other chemical sensitizers, e.g., quaternary ammonium or phosphonium salts as well as ternary sulfonium salts, reducing agents such as stannous salts, polyamines such as diethylene triamine or sulfur compounds as described in US. Patent 1574,- 944. Furthermore, the given emulsions may contain, for the purpose of chemical sensitization, salts of noble metals such as ruthenium, rhodium, palladium, iridium, platinum or gold, as described in the article by R. Koslowsky, Z. Wiss. Phot. 46, 6572 (1951).

Furthermore, the emulsions may contain stabilizers such as homopolar or salt-type compounds of mercury which contain aromatic or heterocyclic rings (e.g., mercaptotriazoles), simple mercury salts, sulfonium-mercury double salts and other mercury compounds. Other suitable stabilizers are azaindenes, preferably tetra or pentaaza- 'indenes, especially those substituted with hydroxy or amino groups. Such compounds have been described by Birr, Z. Wiss. Phot. 47. 2-58 (1952). Other suitable stabilizers include heterocyclic mercapto compounds such as phenylmercapto-tetrazole, quaternary benzthiazole derivatives and benztriazoles.

The emulsions may also contain optical sensitizers such as the usual polymethine dyes such as neutrocyanines, basic or acid carbocyan'ines, rhodacyanines, her'nicyanines, styryl dyes and oxonoles. Examples of these sensitizers have been described in the work by F. M. Hamer The Cyanine Dyes and Related Compounds (1964).

The emulsions may be hardened in the usual manner, for example, using formaldehyde or halogen-substituted aldehyde which contain a carboxyl group, e.g., mucobromic acid diketones, methane sulfonic acid ester and dialdehydes.

EXAMPLE 1 600mg. of saponin as wetting agent,

200 mg. of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene as stabilizer and 10 ml. of a 10% aqueous solution of formaldehyde were added to a silver iodobromide gelatin emulsion which contained 60 g. of silver per liter in the form of silver halide and had a silver iodide content of 6 mols percent.

This emulsion was divided into 14 equal parts and the following substances added to the individual parts: Sample 1Comparison sample without additive Sample 2750 mg. per mol of silver halideof the sensitizer of the following formula (described in German patent specification 1,178,297);

Sample 3l g. per mol of silver halide of ethylene-bis- (di-n-butylsulfonium)-dibr0mide as described in US. Patent No. 2,288,226.

Sample 4--1 g. per mol of silver halide of compound I Sample 51 g. per mol of silver halide of compound IV Sample 6-1 g. per mol of silver halide of compound V Sample 7.1 g. per mol of silver halide of compound IX Sample 8-1 g. per mol of silver halide of compound X Sample 91 g. per mol of silver halide of ethylene-bisdi-n-butylsulfonium-dibromide and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 101 g. per mol of silver halide of compound I and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 1l--1 g. per mol of silver halide of compound 1V and 750 mg. per mol of silver halide of a polyethylene oxide derivatives of the type added to Sample 2.

Sample l21 g. per mol of silver halide of compound V and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 13-1 g. per mol of silver halide of compound IX and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 14 -1 g. per mol of silver halide of compound X and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample'2.

The results of the comparison tests are shown in the following table:

TABLE 1 Developed for 6 minutes EXAMPLE 2 The procedure employed was the same as that described in Example 1. The emulsion was divided into 7 parts and the following substances were then added to the different parts of the emulsion:

Sample lComparison sample without additive.

Sample v2750 mg. per mol of silver halide of an ionic polyalkylene oxide derivative which corresponds to the following formula (as described in German patent application No. A $0,595) corresponding to US. application Ser. No. 591,974, filed Nov. 4, 1966:

Sample 3l g. per mol of silver halide of ethylene-bis-(din-butylsulfonium)-dibromide and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 41 g. per mol of silver halide of Compound I and 750mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 5-1 g. per mol of silver halide of Compound V and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 6-1 g. per mol of silver halide of Compound IX and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 71 g. per mol of silver halide of Compound X and 750 mg. per mol of silver halide of a polyethylene oxide of the type added to Sample 2.

The results of the comparison tests are shown in the following table:

TABLE 2 Developed for 6 minutes Sample:

1 Control... 0. 68 0. 06 2 +3.0 0.65 0. 06 0. 64 0 07 0. 65 0 09 0. 60 0. 07 0. 63 0. 10 0. 65 0. 07

EXAMPLE 3 The procedure employed was the same as that described in Example 1. The emulsion was then divided into 4 parts and the following substances were then added to the different parts of the emulsion:

The results of the comparison tests are shown in the following table:

TABLE 3 Developed for 6 minutes D 'y S Sample:

1 Control... 0. 68 0. O6 2 +1.5 0.55 0.07 3 +1.5 0 52 0.06 4 +2.0 0 55 0.06

EXAMPLE 4 40 mg. of the panchromatic sensitizer of the following formula:

8 And 20 mg. of the orthochromatic sensitizer of the following formula:

were added per liter, to the same emulsion as used in Example 1, the emulsion was then divided into 9 equal parts. The following compounds were added to the different parts:

Sample 1Comparison sample without additive,

Sample 2-750 mg. per mol of silver halide of a compound of the type described in German patent specification specification No. 1,178,297 (see Example 2 of Example 1).

Sample 3-750 mg. per mol of silver halide of the sensitizer of compound No. VII of Sample 2 of Example 2.

Sample 4-1 g. per mol of milver halide of compound No. IV.

Sample 5-100 mg. per mol of silver halide of compound No. IV and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 2.

Sample 6l mg. per mol of silver halide of com pound No. IV and 750 mg. per mol of silver halide of a polyethylene oxide of the type added to Sample 3.

Sample 7-1 g. per mol of silver halide of compound No. VII.

Sample 8-1 g. per mol of silver halide of compound No. VII and 750 mg. per mol of silver halide of a polyethylene oxide derivatitive of the type added to Sample 2.

Sample 9l g. per mol of silver halide of compound No. VII and 750 mg. per mol of silver halide of a polyethylene oxide derivative of the type added to Sample 3.

The samples were applied onto a cellulose acetate support and developed as in Example 1.

TABLE 4 Developed for 6 minutes D 'y S Sample 1 Control..- 0. 0. 06 2 80 0. 08 95 0. 07 0. 06 75 0. 07 0. 06 0. 07 80 0. 07 80 0. 08

R=hydrogen, alkyl having up to 18 carbon atoms, aeyl derived from an aliphatic carboxylic acid having up to 18 carbon atoms, a phenyl ring;

(B) a condensation product of spirocyclic pentaerythritol-diphosphoric acid and polyethylene glycols;

(C) a condensation product of amidophosphoric acid with polyethylene glycols and (D) a quaternation product of tertiary polyamines with bifunctional polyalkylene oxides.

with a sensitivity increasing amount of a disulfonium salt 5 having the formula wherein:

R=a branched or unbranched alkyl or alkenyl radical containing up to 6 carbon atoms and substituted by at least one hydroxyl, carboxyl or epoxy group;

Z=an alkylene radical having up to 18 carbon atoms that can be substituted with at least one hydroxyl, carboxyl or epoxy group, and can be interrupted by at least one oxygen atom, or aralkylene; and

X=an anion.

2. The combination of claim 1 wherein R represents a hydroxyl substituted ethyl group.

3. The combination of claim 1 in which the cation of the sulfonium salt has the formula CHiOHzOH CHgCHgOH 4. The combination of claim 1 in which the cation of the sulfonium salt has the formula 5. The combination of claim 1 in which the cation of sulfonium salt has the formula References Cited UNITED STATES PATENTS 2,848,330 8/1958 Chechak et a1. 96-108X 25 NORMAN G. TORCHIN, Primary Examiner R. E. FICHT ER, Assistant Examiner 

